Hydrogen production through the splitting of water has attracted great scientific interest due to its relevance to renewable energy storage and its potential for creating an energy carrier free of carbon dioxide emissions. Electrocatalytic systems for H2 generation typically incorporate noble metals such as platinum (Pt) in the catalysts because of their low overpotential and fast kinetics for driving the hydrogen evolution reaction (HER). However, the high cost and limited world-wide supply of these noble metals makes their use an obstacle to a viable commercial process. Several non-noble metal materials, such as transition metal chalcogenides, carbides and complexes, as well as metal alloys have been widely investigated recently, and characterized as catalysts and supports for application in hydrogen evolution.
Early transition metal nitrides have been demonstrated to have excellent catalytic activities in a variety of reactions. One of the primary interests in the applications of nitrides in these reactions was to use them in conjunction with cheaper alternative metals to replace group VIII noble metals. For example, the function of molybdenum nitride as a catalyst for hydrocarbon hydrogenolysis resembles that of platinum. The catalytic and electronic properties of transition metal nitrides are governed by their bulk and surface structure and stoichiometry. While there is some information concerning the effect of bulk composition on the catalytic properties of this material, there is currently very little known about the effects of surface nanostructure.
Ni and NiMo are known electrocatalysts for hydrogen production in alkaline electrolytes, and in the bulk form have exhibited exchange current densities between 10−6 and 10−4 A cm−2, compared to 10−3 A cm−2 for Pt (Huot, et al., (1991) J. Electrochem. Soc. 138:1316-1321). Jak{hacek over (s)}ić et al. ((1998) Int. J. Hydrogen Energy 23:667-681) and Jak{hacek over (s)}ić, M. M. ((2001) J. Hydrogen Energy 26:559-578) postulated the hypo-hyper-d-electronic interactive effect between Ni and Mo yields the synergism for the HER. Owing to their poor corrosion stability, few studies in acidic media have been reported.
Owing to these and other disadvantages in the current state of the art, a more affordable and efficient method for hydrogen production is needed.